Brake mechanism



March 24, 1936. M.'| ouGHEAD BRAKE MECHANISM Original Filed March 7, 1929 3 Sheets-Sheet l March 24, 1936.

' M. LOUGHEAD BRAKE MECHANISM Original Filed March 7, 1929 43 Sheets-Shea Original Filed March 7, 1929 M; LOUGHEAD l BRAKE MECHANISM 3A Sheets-Sheet 3 mug/mil "all EE) lili- Iii".

Patented Mar. 24, 1936 PATENT OFFICE BRAKE IVIECHANISM Malcolm Loughead, Mokelumne Hill, Calif., assignor to Hydraulic Brake Company, Los Angeles, Calif., a corporation of California Application March '1, 1929, Serial No. 344,998 Renewed May 19, 1934 s claims. (c1. so-54.6)

My invention relates to a. brake mechanism and more particularly to a hydraulically operated brake system.

In certain types of automobiles it is desirable to have the supply reservoir and fluid pressure mechanism in one compact unit in order to require as little space as possible and effect a large economy in the time required to install the system in an automobile. Hydraulic brake systems are often made by a manufacturer of such systems and installed in automobiles by the manufacturer of the automobile. The facility with which a brake system may be installed in a car is therefore an important feature.

An object of the invention is to provide a new and improved pressure and supply unit for hydraulic brake systems.

A further object is to provide a reservoir and cylinder unit which is readily attachable to a vehicle.

A further object is to provide a pressure and supply unit in which the actuating mechanism for the piston contacts with the piston through the open end of the cylinder.

A further object is to provide a pressure and supply unit having a piston provided with a fluid seal to prevent air from entering the cylinder.

A further object is to provide a pressure and supply unit in which a large and direct communication is established between the fluid seal of the piston and the reservoir, permitting air entering the fluid seal readily to pass into the reservoir.

In accordance with the general features of the invention, an integral reservoir and cylinder is provided in which the fluid from the reservoir is in direct and constant communication with a fluid seal surrounding the piston, permitting the 4rearward end of the piston to be exposed to atmospheric pressure without danger of entrapping air in the cylinder.

Referring to the drawings:

Fig. l is a cross-section of the pressure and supply unit embodying my invention;

Fig. 2 is a sectional plan view taken on lines 2 2 of Fig. 1;

Fig. 3 is an end elevation, partly in section, taken on lines 3-3 of Fig. 1;

Fig. 4 is an end elevation, partly in section, taken on line 4-4 of Fig. 1;

Fig. 5 is a schematic view of the hydraulic brake system embodying the invention; and

Fig. 6 illustrates a modified form of the invention.

The apparatus comprises, in general, a reservoir II having .a cylinder I2 cast integrally therewith and a piston I3 exposed rearwardly to atmospheric pressure and movable forwardly by a plunger I4 actuated by a foot pedal I5.

The piston I3 has an annular recess I6 of such length as to be in constant communication with a plurality of passages I'I leading into the uid reservoir and thus forming a fluid seal about the piston. The piston has a. reduced portion I8 which terminates in an outwardly projecting flange I9. A packing ring 22 is clamped between a collar 23 and the flange I9 for retaining the packing ring in contact with the cylinder wall and allowing the forward end of the packing ring to resiliently engage the cylinder wall. An end ring 24 secured in position by a split ring 25 is provided to prevent the Withdrawal oi'l the piston from the cylinder.

In order to exclude dust and other extraneous matter from the piston a boot 26 is retained by an annular collar 21 within an annular groove in the outer cylinder wall, the other end of the boot being attached to plunger I4 by a collar- 28 which similarly retains this end of the boot in a groove 29 in the plunger. The boot is provided with an aperture 32 in its lower side to permit free access of air into and from the boot to compensate for changes of volume within the boot so that the rearward end of the piston will at all times be subject to atmospheric pressure.

A plurality of passages 33 lead from the annular recess in the piston into cylinder I2. The face of the piston is provided with a packing cup 34 which is adapted to cover passages 33 during the protractile stroke of the piston to cut 01T communication between the recess and the cylinder during the pressure stroke of the piston. During the retractile stroke of the piston the low pressure within the cylinder causes packing cup 34 to be unseated and allow fluid from recess I6 to flow by the packing cup into the cylinder. The piston is moved to its retracted position by a spring 35 which also serves to urge a valve 36 against valve seat 31 in the forward end of the cylinder." A second valve 38 is mounted concentrically in valve 36 and is retained in its closed position by a spring 39. l

In the application of the brakes the piston is moved forwardly to produce a fluid pressure in the cylinder, causing valve 38 to open and allow uid from the cylinder to pass into an exit chamber 42 which leads to a plurality of pipes 43 connected to the wheel brake cylinders 44. In

releasing the brakes pedal I5 is allowed to return ya wall 61 of the vehicle.

the piston to its normal position. 'I'he area of valve 36 is so related to the area of the face of the piston that a positive fluid pressure will be maintained in the iiuid lines 43 and wheel brake cylinders 44. As spring 35 tends to retract the piston a low pressure will be created within the cylinder and as the rear face of the piston is subject to atmospheric pressure a positive pressure of six pounds per square inch above atmospheric pressure will be maintained in the iluid pressure lines on account of the smaller area of valve 36. Thus it will be impossible for the retraction of the piston to cause a negative pressure in the iluid lines or wheel brake cylinder which might cause air to enter the wheel brake cylinders and interfere with the proper operation of the brake system. On account of the retardation of the return of the iiuid to cylinder I2 and the low pressure caused in cylinder I2 thereby, fluid will flow from recess I6 through passages 33 into the cylinder during the retraction of the piston, producing an excess of fluid in the cylinder after the piston is retracted. This excess of fluid passes through an aperture 45 which is immediately in front of the retracted position of the piston into the iiuid reservoir, as the fluid from the wheel brake cylinders returns to the master cylinder, thus assuring that the master cylinder will always be filled to capacity with brake fluid.

It will be noted that the low pressure in the cylinder will not be communicated to the packing ring 22 on account of the fluid seal around the piston which is in communication with the reservoir and the uid passing from the fluid seal into the cylinder will be immediately replaced by fluid from the reservoir. However, if any air should pass by the packing ring 22 into the uid seal it will rise to the top of the uid seal and pass through one of the passages I1 into the uid reservoir.

The top of the iluid reservoir is provided with a valve 52 which serves to admit air into the cylinder as the supply of fluid declines and excludes dust and foreign matter from the reservoir. Valve 52 comprises a hollow cap 53 having an aperture 54 therein. A valve stem 55 extends through aperture 54 and serves to hold a diaphragm valve 56 against seat 51 formed by the periphery of cap 53. The upper end of stem 55 is provided with a plurality of punched-out portions 55' which serve to prevent the stem from being withdrawn from aperture 54. As the amount of iluid within the reservoir decreases diaphragm 56 will be forced downwardly by atmospheric pressure to admit an amount of air corresponding to the decrease in the amount of uid.

The forward end of cylinder I2 is spaced a suflicient distance from the forward wall of the reservoir to provide space for the discharge chamber 42 between the end of the cylinder and the forward wall of the unit. A plurality of plugs 6I, 62, and 63 are threaded into discharge chamber 42 and make connection with the uid pressure lines 43. Plugs 6I and 62 lead to the i'rontV brakes of the vehicle and plug 53 leads to the rear brakes.

The rear end oi.' the unit is provided with a downwardly projecting flange 64. In attaching the unit to a vehicle the cylindrical portion 65 of the unit which extends rearwardly from the unit is placed in a similarly shaped aperture 66 in through wall 61 and flange 64 and s'erve to retain the unit firmly attached to the wall.

Fig. 6 illustrates a modiiied form of the invention in which the piston I3' is provided with an A pair of bolts 68 pass annular recess 10. 'Ihis recess is connected through passages 1I to the interior of the piston, connecting the interior of the piston through passages I1 with the iluid reservoir. A plunger 12 is attached to the piston by a ball and socket joint 13. 'I'he rear side of the piston is enclosed by a boot 14, one end of which is provided with an annular bead secured to the plunger by a nut 16 which forces the annular bead against an undercut shoulder 11 formed upon the plunger. The other end of the boot is provided with a radiallyextending ange 18 which is secured by a plate 19 and screws 8| to the rear end of the cylinder. The boot 14 thus forms a fluid chamber which is constantly maintained full of fluid from the iiuid reservoir which passes through passages l1 into the annular recess 10 through passages 1| into the interior of the piston and past ring 24', which limits the rearward movement of the piston. The clearance between the plunger 12 and ring 24 is suiiicient to allow free communication of fluid with the boot. Connection with the actuating lever I5 is made through a rod 82 which engages a tubular bore within the plunger, allowing the lever l5' to return to its normal position without positively retracting plunger 12.

The operation of this embodiment of the invention is similar to that shown in the previous iigures. In this embodiment it is impossible to produce a lower than atmospheric pressure within the iluid chamber formed by the boot, due to the fact that when liquid is drawn into the master cylinder upon the retractile movement of the piston. the boot will contract when iiuid is drawn therefrom without producing a lower than atmospheric pressure therein. Furthermore, the fluid drawn into the master cylinder during the retractile movement of the piston will be constantly replaced by iiuid from the fluid reservoir with the result that no air can leak into the master cylinder from the rearward end` of the piston, in spite of the fact that mechanical connection is made between the actuating lever and the piston to actuate the piston within the master cylinder.

Having described the nature and embodiments of my invention, what I desire to secure by United States Letters Patent is as follows: v

1. In a hydraulic brake mechanism, a cylinder, a iiuid supply reservoir mounted thereon', a piston slidably mounted in the cylinder and having an annular recess, an aperture in the wall of the reservoir communicating with the recess and forming a fluid seal, a packing ring surrounding the piston rearwardly of the fluid seal, a packing cup carried by the face of the piston, said piston having a. passage between the recess and the cylinder and normally covered by the packing cup, said reservoir having an aperture immediately in front of the retracted position of the piston, a double acting check valve at the discharge end of the cylinder for retarding the return flow of fluid to the cylinder, means for moving the piston forward to produce a fluid pressure in the cylinder, and a spring for retracting the piston causing va low pressure in' the cylinder where iiuid from the reservoir passes into the cylinder through the annular recess'and passage in the piston.

2. In a hydraulic brake mechanism, a cylinder having a cylindrical bore, an integral cap for the end of the cylinder having a smaller bore forming a shoulder to provide a valve seat, a discharge tube threaded into the integral cap and leading into the smaller bore, a double check sure, an aperture interconnecting thefreservoir.

aosaars valve adapted to engage said valve seat, a piston movable in the cylinder and having an annular recess, a fluid supply reservoir mounted on the cylinder communicatingwithsaid recess, means engaging the piston for moving the piston forward to produce a uid pressure, and a spring for retracting the piston and yieldingly urging said valve to its seat to retard the return of the liquid to the cylinder. e

3. In a hydraulic brake mechanism, a cylinder `and reservoir comprising a unit having a plurality of Walls, the end o1' the'cylinder being spaced from the front wall of the unit to provide a. discharge chamber therebetween, a piston movable in the cylinder, a double acting valve interposed between the cylinder andthe' discharge chamber, a spring having one end engaging the piston and the other end engaging the valve, and means for positively moving the piston forward to produce a iuid pressure in the cylinder, said spring acting to retract the piston and ylelding'ly urge the valve forward to maintain a positive pressure inthe discharge chamber.

4. In a hydraulic brake mechanism, a cylinder and reservoir unit comprising a cylinder and reservoir integrally cast, a piston having an annular recess and movable within the cylinder, having its rear end exposed to atmospheric presand said recess, a passage in the pistonconnecting the recess with the cylinder, a packing cup carried by the piston for closing said passage ately in front ofthe retracted position of the enter the cylinder through the passage in the piston, .the excess fluid being returned to the reservoir when the piston is completely retracted.

5. In a. uid pressure mechanism of thel class described, a cylinder having a cylindrical bore,

.means for closing said passageway during the forward stroke of the piston but permitting ow therethrough during its return stroke, means engaging the piston for moving the piston forward to produce a fluid pressure, a spring for retracting the piston and yieldingly urging said valve to its seat to retard the return of the liquid to the cylinder, a iiexible boot enclosing the rear of said piston, said boot having its interior in communication with said passageway whereby iiuld can flow from th/e interior of the boot through said passageway during the return stroke of the piston, and a fluid reservoir communicating with the interior of said boot.

6. In hydraulic mechanism of the class de- "scribed, a cylinder and reservoir comprising a unit having a plurality of walls, the end of the cylinder being spaced from the front wall of the unit to provide a discharge chamber therebetween, a piston movable in the cylinder, a doubleacting valve interposed between the cylinder and the discharge chamber, a spring having one end engaging the piston and the other end engaging the valve, means forpositively moving the piston forward to produce a iiuid pressure in the cylinder, said spring acting to retract the piston and yieldingly urge the valve forward to maintain a positive pressure in the discharge chamber durlng the retraction of the piston, said piston hav- 'ing a passageway therethrough, means for clos-l ing said passageway during the forward stroke of the piston but permitting flow through said passageway during the return stroke of the piston, a flexible boot enclosing the rear of said piston and communicating with said passageway whereby uid can ow from the interior of the boot through-said passageway during the return stroke of the piston, and a iluid reservoir communicating with the interior of said boot.

Y MALCOLM LOUGHEAD. 

